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 * The Universal Permissive License (UPL), Version 1.0
 *
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 * person obtaining a copy of this software, associated documentation and/or
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 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
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package com.oracle.truffle.regex.tregex.buffer;

public final class IntRingBuffer {

    private final int[] buf;
    private int start = 0;
    private int length = 0;

    public IntRingBuffer(int sizePowerOf2) {
        buf = new int[1 << sizePowerOf2];
    }

    public boolean isEmpty() {
        return length == 0;
    }

    public void clear() {
        start = 0;
        length = 0;
    }

    private int index(int index) {
        assert Integer.bitCount(buf.length) == 1;
        return (start + index) & (buf.length - 1);
    }

    public int first() {
        assert !isEmpty();
        return buf[start];
    }

    public int last() {
        assert !isEmpty();
        return buf[index(length - 1)];
    }

    public void add(int i) {
        assert length < buf.length;
        buf[index(length++)] = i;
    }

    public void addAll(int[] o) {
        assert buf.length >= length + o.length;
        int copyStart = index(length);
        int copyLength = o.length;
        if (copyStart + copyLength > buf.length) {
            copyLength -= (copyStart + copyLength) - buf.length;
            System.arraycopy(o, copyLength, buf, 0, o.length - copyLength);
        }
        System.arraycopy(o, 0, buf, copyStart, copyLength);
        length += o.length;
    }

    public int removeFirst() {
        assert !isEmpty();
        int first = first();
        start = index(1);
        length--;
        return first;
    }
}
